The present invention relates to the general field of treating skin cosmetically or medically by means of laser radiation.
The invention relates particularly to producing heat at the surface of the skin by subjecting a composition comprising at least one chromophoric agent to laser radiation, such a composition being referred to below as a xe2x80x9cchromophoric compositionxe2x80x9d.
The chromophoric agent(s) absorb(s) light energy from the laser radiation so as to transform said energy into heat and/or so as to modify the chemical structure(s) of the agent(s) under the effect of the laser radiation.
Trials performed by irradiating a chromophoric composition with a laser have shown that it is possible to raise skin temperature locally to more than 100xc2x0 C. so as to obtain tissue volatilization optionally associated with dermis coagulation.
In the trials, the chromophoric composition was sprayed onto the skin by means of a spray gun, which makes it very difficult to obtain a uniform deposit.
An object of the present invention is to improve the efficacy of cosmetic treatment or medical treatment that uses a chromophoric composition that is subjected to laser radiation.
The present invention achieves this object by providing a device including a chromophoric composition and making it possible to apply the chromophoric composition to the skin, wherein the chromophoric composition is in the form of a layer of constant thickness bonded to one face of backing, at least prior to being applied to the skin, the chromophoric agent or agents being distributed uniformly in said composition, and the type of the composition being chosen such that, under the effect of laser radiation, light energy from the laser radiation is transformed locally into heat and/or the chemical structure(s) of the chromophoric agent(s) is/are modified locally.
The invention makes it easy to deposit a constant thickness of chromophoric composition on the surface of the skin.
The thickness of chromophoric composition on the surface of the skin determines the extent to which the laser radiation is absorbed.
The fact that, in the invention, the thickness of the chromophoric composition is constant and known in advance offers the advantage that the absorbance of the chromophoric composition is defined exactly, and therefore so is the quantity of heat produced on irradiating the composition with the laser radiation.
Thus, the effects of the laser radiation treatment are easier to determine, and the treatment is also easier to reproduce.
An additional advantage of the invention lies in the fact that, since the chromophoric composition is not sprayed, there is no danger of it being dispersed into the atmosphere and being deposited elsewhere than on the region of the skin that is to be treated.
In a particular embodiment, the device includes one or more substances that are in the inactive state in the absence of laser irradiation, and that, under the effect of the laser irradiation, are suitable for transforming into and/or releasing active substances producing effects on the skin.
The invention also provides a method of fabricating a device making it possible to apply a chromophoric composition to the skin, said method including a step consisting in forming a layer of constant thickness of a chromophoric composition, the type of the composition being chosen such that, under the effect of laser radiation, light energy from the laser radiation is transformed locally into heat and/or the chemical structure(s) of the chromophoric agent(s) is/are modified locally.
Preferably, the method includes a step consisting in bonding backing to a layer of determined thickness of a chromophoric composition, at least temporarily.
The invention also provides a method of transforming light energy from laser radiation into heat at the surface of the skin by means of a chromophoric composition, and/or of modifying the chemical structure(s) of one or more chromophoric agents contained in a chromophoric composition at the surface of the skin, said method comprising steps consisting in:
applying a layer of a chromophoric composition to the skin, which layer is of constant thickness and is bonded to backing, at least prior to being applied to the skin, the chromophoric agent(s) being distributed uniformly in said composition;
removing said backing if it is not transparent to the wavelength of the laser used; and
irradiating said chromophoric composition by means of a laser, the laser irradiation making it possible to transform light energy from the laser radiation into heat in said layer of chromophoric composition, and or to modify the chemical structure(s) of the chromophoric agent(s), said chromophoric composition having absorbance that, at the emission wavelength of the laser, is such that the light energy transmitted into the skin via said layer of chromophoric composition does not cause any undesired irreversible damage to the tissue or to the cells.
The invention also provides the use of at least one chromophoric agent in fabricating a composition designed to be applied to the surface of the skin, and then to be subjected to laser radiation, the chromophoric composition being in the form of a layer of constant thickness, subjecting said composition to laser irradiation making it possible for light energy from the laser radiation to be transformed locally into heat and/or for the chemical structure(s) of the chromophoric agent(s) to be modified locally.
The invention also provides a method of performing cosmetic treatment, in particular for reducing wrinkles, said method including a step consisting in:
applying a chromophoric composition to the surface of the skin, said composition being in the form of a layer of constant thickness, and the type of the composition being chosen such that, under the effect of laser radiation, the light energy is transformed locally into heat and/or the chemical structure(s) of the chromophoric agent(s) is/are modified locally.
Prior to being applied to the skin, the layer of chromophoric composition may be cut to the format of the region to be treated.